The conventional shock-absorbing device for bicycles is focused on absorbing shocks transferred from the road to improve the comfort of the users in the vehicle.
The bicycle shock-absorbing devices include the front shock-absorbing device and the rear shock-absorbing device, and both of which can be operated by hydraulic or pneumatic media, or both.
Taiwan Utility Model Patent Application No. 098217431 discloses a first cylinder having a first installation end and a first open end, wherein the first installation end is connected to the bicycle frame. A piston rod is received in the first installation end. The piston rod includes a first end and a second end, wherein the first end is connected to the first installation end and the second end of the piston rod is connected with a first piston. A second cylinder has a second installation end second open end, wherein the second installation end is connected to the bicycle. The second cylinder has liquid received therein and the second open end of the second cylinder smoothly extends into the first open end of the first cylinder. The second end of the piston rod and the first piston smoothly extend into the second open end of the second cylinder. The second open end of the second cylinder is connected with a second piston and a room is defined in the first cylinder and located between the second piston and the first installation end. A spring is located in the room and includes a first end and a second end. The first end of the spring contacts the first cylinder and the second end of the spring contacts the second cylinder. A biasing member is located in the room in the first cylinder.
U.S. Pat. No. 7,607,522 discloses a shock-absorbing device which has a main piston, and a piston rod extends through the main piston and located between two tubes sharing a common center. The two tubes have liquid received therein. The main piston has a compression portion and an expanding portion, and the two tubes include an interior portion and an exterior portion. A valve is located to control the liquid. A first adjustment device is connected to the compression portion and a second adjustment device is connected to the expanding portion. A first pressurizing device uses a piston to compress the media and separate the liquid. The second adjustment device further includes a first valve and a first non-one-way valve. The first valve and the first non-one-way valve are located in a pipe which is located between the compression portion and the first pressurizing device. A second valve and a second non-one-way valve are located in another pipe which is located between the expanding portion and the first pressurizing device.
In the first example, the biasing member and the spring are compressed to absorb the shocks. When the shock-absorbing device expands, the biasing member and the spring separate the first and second cylinders, and the piston rod moves relative to the second cylinder to provide damping effect. The second example uses the movement of the main piston and the piston rod to provide different damping effects when the shocks are applied to the shock-absorbing device. The adjustment device adjusts the damping coefficient to provide the ideal shock-absorbing result.
However, the liquid in the second cylinder which is a single cylinder and the spring has fixed spring force, so that when minor shocks are applied to the shock-absorbing device of the first example, the spring is not responsive to the minor shocks which are transferred to the cyclist directly. For the second example, the shock-absorbing features can be adjusted by the two tubes and the adjusting device to respond to the large or minor shocks. The speeds that the rear shock-absorbing device expands and retracts are the same. In other words, when operation, the change of the shock-absorbing device is too fast that makes the cyclist feel uncomfortable. Besides, the shock-absorbing device involves complicated structure which is difficult to manufactured and heavy. The two tubes have leakage problem which makes the shock-absorbing device cannot function as desired.
The present invention intends to provide a shock-absorbing device which improves the shortcomings of the existed shock-absorbing devices.